Storm windows were initially developed as an auxiliary closure to be installed about the exterior side of a primary window unit commonly found in homes and buildings. These storm windows were adapted to be utilized during the cold months of the year to insulate primary windows against wind, moisture and cold.
The first storm windows, for example, may have been nothing more than a piece of sheet metal that was patterned to cover the entire exterior opening of a preexisting primary window. This method functioned to insulate primary windows, however, the disadvantage is obvious of using an opaque material. Therefore, storm windows were developed which incorporated a glass pane supported by a frame which was attached about the exterior side of the primary window unit. This type of storm window not only insulated the primary window unit but also permitted light to enter the home or building. However, this large pane was awkward to install and since it did not incorporate a movable sash, it had to be taken down in order to ventilate the home or building on mild days which may occur during the winter months. Later storm windows have incorporated movable sashes which permitted the storm window to be left in place year around because the lower sash of the storm window could be raised and locked in place thereby allowing ventilation of the building or home when the primary window unit was opened.
In the past storm windows were used primarily in the northern latitudes to insulate primary windows during the winter months. But, in recent years the energy crisis has prompted homeowners situated in all temperature zones to employ storm windows in both the winter and summer months to increase the efficiency of both heating and air conditioning systems. Therefore, a great deal of importance is now being placed on the development of newer and more effective storm window systems.
It is of particular interest to note that many buildings constructed prior to the last five years were not designed with energy conservation in mind. For instance, many high rise office buildings were given an attractive exterior veneer of plate glass which provided little insulation for the building and necessitated the installation of heating and air conditioning units of large capacities.
The energy crisis and subsequently the increased cost of energy is causing building owners to seek out ways to renovate existing buildings such that heating and air conditioning demands are effectively reduced. On buildings with a large amount of single layer glass, it appears that storm windows are the obvious solution. However, storm windows that are installed about the exterior of a building especially a high rise building are expensive to install and difficult to maintain. Additionally, the exteriorly installed storm window may drastically alter the appearance of the building on which they are placed.
Another consideration to be taken into account when discussing the application of storm windows to preexisting primary windows is whether or not the storm window system is adaptable to various primary window systems having a variety of movable sashes. This is of particular importance when it is appreciated that primary windows may be of the hopper, awning, or pivot type as well as any combination thereof. It should be appreciated that unobstructed movement of the primary window is necessary in order to facilitate periodic maintenance or repair of the same.